Apparatus and method for drilling wells



March 19, 1968 v. D. s'ToNE APPARATUS AND METHOD FOR DRILLING WELLS 5Sheets-Sheet 1 Filed April 21, 1964 INVENTOR. V/QG/L 0. STONE ATTORNEY.

March 19, 1968 v. D. STONE APPARATUS AND METHOD FOR DRILLING WELLS 3Sheets-Sheet 3 Filed April 21, 1964 I N VENTOR WQG/L 0. STONE k v Arra/VEK A March 19, 1968 v. D. STONE APPARATUS AND METHOD FOR DRILLINGWELLS 3 Sheets-Sheet 5 Filed April 21,1964

INVENTOR. V/RG/L 0. 570M? ATTORNEK United States Patent 3,373,806APPARATUS AND METHOD FOR DRILLING WELLS Virgil D. Stone, Morgan City,La., assiguor to Gulf Oil Corporation, Pittsburgh, Pa. Filed Apr. 21,1964, Ser. No. 361,447 18 Claims. (Cl. 166.5)

This invention relates to oil and gas wells drilled in underwaterlocations, and more particularly to a method and apparatus for drillingand completing such wells.

Oil wells have been drilled and completed in offshore locations in wateras deep as about 200 feet. If the offshore well is a wildcat well, amobile rig is often preferred because such a rig can readily be moved toanother location if the well should be a dry hole. If an offshore wellin water deeper than about 50 feet should prove to be productive, it isnecessary to keep the mobile rig on location to brace the well until asuitable platform for support of the wellhead assembly can beconstructed. The cost of platforms for hanging casing and supporting thewellhead assembly increases rapidly with increases in depth of thewater. For example, a platform for use in water 350 feet deep isestimated to cost approximately $2,000,000. It is apparent thatplatforms for wells in water of that depth will be built only after ithas been established that the well has penetrated a reservoir containinga substantial amount of oil. However, rental for a rig capable ofdrilling in water of that depth i approximately $8,500 a day; hence anydelay in installing a platform to support the well will cause largerental charges while the rig merely braces the casing.

One method that has been suggested for eliminating the cost of platformsto support the wellhead structure is to install the wellhead at orslightly above the botom of the body of water. In shallow locations,conventional wellhead structures can be installed on the well underwaterby divers. Such installations are limited to wells in shallow water inwhich the pressure allows the divers to work safely.. Ordinarily, thecost of platforms supporting wells in shallow water is not excessive.Special wellhead connections and apparatus allowing the wellheadassembly to be installed by remote control have been suggested for useon wells completed at depths below those at which divers can safelywork, but the many problems inherent in installing a wellhead assemblyby remote control have greatly increased the cost and hazards of suchwell completions.

Moreover, it is desirable that the well and the flow lines from the wellbe readily accessible for servicing. For example, deposition of paraffinfrom the flow lines of a well to the separator can quickly plug a welland seriously reduce production from the well. In some areas in whichthe productive sands are unconsolidated, the flow lines of the well maybecome quickly plugged with sand. Both sanding and paraffin depositionfrequently occur in wells drilled in the Gulf of Mexico off theLouisiana coast, an area in which drilling in deep water is mostprevalent. The installations of wellhead assemblies at or near thebottom of the ocean floor by the techniques heretofore suggested haveleft the wells in a condition such that servicing was difficult.

This invention resides in a method and apparatus for completion of wellsdrilled in formations under Water more than fifty feet deep and whichmay be as much as 600 feet deep. The method and apparatus areparticularly advantageous for the completion of wells in deep waterranging from 100 to 600 feet deep. In this invention, a heavy-walledtube having a diameter large enough to permit a man to be loweredthrough it and install a wellhead assembly is forced, either before orafter the well is drilled,

into the ground at the bottom of the body of water, hereinafter referredto as the ocean floor, surrounding the well to a depth adequate toexclude flow of water into the tube. Preferably the tube is driven torefusal into the ocean floor. The tube, herein referred to as a snorkeltube, extends upwardly above the surface of the water. After the well isdrilled, casing set, and the tube is in place, water is pumped from thesnorkel tube to permit access to the well at any desired level above theocean floor for the installation of conventional wellhead apparatus andflow lines by workmen who work at atmospheric pressure. The snorkel tubeprovides a support for the flow lines from the well and the necessaryequipment for production of oil from the well. In one embodiment of theprocess of this invention particularly suitable for use in wildcatwells, a well is drilled and tested by any desired means, and thereafterthe snorkel tube is driven into the ocean floor only when a producingwell is assured.

Referring to the drawings:

FIGURE 1 is a diagrammatic view partly in vertical section of a welldrilled by a mobile rig after testing and prior to cutoff of the upperportion of the well;

FIGURE 2 is an elevational view, partially in vertical section, showingthe well illustrated in FIGURE 1 at an intermediate stage of completionwith the snorkel tube and supporting structure in place;

FIGURE 3 is a diagrammatic view, partially in vertical section, of aWell completed and ready for production of oil;

FIGURE 4 is a horizontal sectional view taken along the section line 44in FIGURE 2; and

FIGURE 5 is a diagrammatic view showing in elevation an embodiment ofthe invention in which the snorkel tube is installed prior to drillingthe well.

Referring to FIGURE 1 of the drawings, a well indicated generally byreference numeral 10 is illustrated extending downwardly below a body ofwater with a mobile drilling rig 12 supported above the well by theocean floor. Mobile drilling rig 12 is shown in FIGURE 1 only forpurposes of illustration. One of the advantages of this invention isthat it is suitable for use with either mobile drilling rigs supportedby the bottom of the body of water or floating drilling rigs. The methodof completing a well in accordance with this invention described withreference to FIGURE 1 is particularly valuable in drilling a wildcatwell in that it permits drilling and testing the well before the expenseof the snorkel 'tube or other supporting structure is incurred. Well 10has the usual thin-walled conductor pipe 14, which may be from about 16to 36 inches in diameter, washed or driven into the ocean floor.Extending downwardly through conductor pipe 14 to a depth depending onconditions encountered in the Well is a string of surface casing 16.Surface casing 16 is cemented in place within the conductor pipe 14 inany suitable manner with the cement displaced to a level 18 slightlyabove the ocean floor 20. The annular space 22 between casing 16 andconductor pipe 14 above level 18 is filled with sand. In the particularwell 10 illustrated in FIGURE 1, a second string of casing 24 is runthrough casing 16 and is cemented in place by a suitable procedure whichis not affected by this invention. In the well illustrated in FIGURE 1 amultiple-stage cementer 26 closes the annulus between the casing 24 andcasing 16 and the annulus above cementer 26 is filled with cement 'tothe height required by conditions encountered in the well and determinedby the usual considerations.

After tests have indicated that the well has penetrated a productivezone which justifies completion of the well, the well 10 is plugged by'the installation of a drillable cement retainer 28 inside casing 24 anda cement plug approximately feet long above the retainer. A second 3drillable cement retainer 39 may be installed above the cement plug.Thereafter, the strings of casing 24 and 16 and the conductor pipe 14are cut above the ocean floor 20 and removed from the upper end of thewell. Cutting of the casing can be accomplished, for example, by meansof a high velocity abrasive slurry.

Referring to FIGURE 2 a snorkel tube support, indicated generally byreference numeral 32, is lowered into position over the stub of well 10and secured to the ocean floor by piles 34. Support 32 has a guidesleeve 36 at its upper end and an annular storage tank 38 at its lowerend. An oil line 40 extends from the upper end of storage tank 38upwardly to the water surface for the delivery of oil into andwithdrawal of oil from the storage tank 38. A vent line 42 at the lowerend of storage tank 38 allows the sea water to flow out of or into thestorage tank as oil is delivered into or withdrawn from the tank.Support 32 may be lowered into place from the drilling rig 12. One ofthe advantages of this invention, however, is that drilling rig 12 canbe moved from its location immediately after the testing of the well toavoid rental charges for the drilling rig while awaiting productionfacilities. The support 32 and a snorkel tube 44 are constructed onlyafter it is decided to complete the well.

The support 32 provides lateral bracing of the snorkel tube at alocation between the ocean floor and the surface of the water. The upperend of the support 32 will preferably engage the outer surface of thesnorkel tube approximately 50 to 100 feet below the surface of thewater. Because at that level the support 32 is not exposed to strongforces created by winds or waves and because the support 32 does notcarry the weight of the wellhead assembly and production equipment, thesupport 32 may be a relatively inexpensive lightweight structure. Theexact location of the upper end of the support will be determinedlargely by the depth of the body of water in which the well is drilled.In some instances, it may be desirable to provide lateral bracing of thesnorkel tube at or even above the surface of the water, but such anarrangement loses some of the advantage over platforms of reduction ofthe area of equipment exposed to wind and wave action. In shallow water,for example 50 feet, the snorkel tube may be used without a supportgiving it lateral bracing. In deeper water a comparison between theadded cost of a snorkel tube of adequate rigidity and the cost of asupport 32 may determined whether or not a support is used, particularlyif storage at the well site is not needed.

The snorkel tube 44 is a heavy-walled tube having a diameter largeenough to permit workers to be lowered through the tube and to install aconventional Christmas tree on the upper end of the casing. Snorkel tube44 should have a diameter of about 36 to 72 inches, preferably 40 to 48inches and a well thickness of approximately to 2 inches. The thicknessof the wall of the snorkel tube is dependent on the depth of water inwhich the tube is used, the tube diameter, and the length of theunbraced upper section of the snorkel tube. For example, a wallthickness of /3 inch is adequate for a 48-inch diameter snorkel tube inwater 100 feet deep while a wall thicknes of more than one inch isrequired for water 350 feet deep. In contrast with platforms which havebeen suggested for supporting wells above the surface of the water, thesnorkel tube exposes only a small area to forces exerted by waves andWind. Thus the heavy-walled snorkel tube, being firmly anchored in theocean floor, and not being subjected to the weight of the casing andwellhead asem'bly, provides a firm support for lightweight productionequipment above the surface of the water.

The snorkel tube 44 is lowered through sleeve 36 around the stub of wellltl and driven, preferably to refusal, into the ocean floor. The snorkeltube is driven or jetted into the ocean floor a distance adequate tosupport the full weight of the snorkel tube and to prevent flow of wateraround the lower end of the snorkel tube and upwardly through the tubeto the level of the mud line even though 4,. the body of water is 200,or more, feet deep. Thereafter, water is pumped from the snorkel tubeand workmen are lowered through the snorkel tube to install conventionalsurface-type wellhead equipment at or slightly above the ocean floor 20.Blowout preventers are connected to the upper end of well 10 and thecement plug retainers 30 and 28 and the cement plug are drilled from thewell. Thereafter the well is completed, for example, as illustrated inFIGURE 3 with a conventional Christmas tree and wellhead assemblyindicated generally by reference numeral 46.

In atypical wellhead assembly illustrated in FIGURE 3, workmen loweredinto the snorkel tube cut off the conductor pipe above the level 18 ofthe cement in the annulus 22 and below the upper ends of surface casing16 and casing 24. The surface casing 16 is then cut off below the upperend of casing 24. A short externally threaded joint 47 of surface casingis welded at 48 to the upper end of the surface casing 16 and easinghead 50 is screwed to the upper end of joint 47.

Casing head 50 has an upwardly opening bowl surface 52 adapted toreceive a casing hanger 54 which slides over the upper end of the secondstring of casing 24 and seats in bowl surface 52. Casing hanger 54 hasinternal slips, not shown in the drawings, which engage the outersurface of the casing 24, as that string of casing is pulled up, andhold casing 2-4 in tension. The casing 24 is then cut off a shortdistance above the upper surface of easing hanger 54 and may, ifdesired, be welded to the casing hanger. A casing spool 56 is secured tothe upper end of the easing head 50 by suitable means. Casing spool 56has a downwardly facing surface adapted to engage the upper surface ofcasing hanger 54. Seal rings 58 and 60 prevent leakage between thecasing hanger and the casing spool and casing head. If desired, tubingcan be run downwardly through casing 24, in which event conventionaltubing hangers will be mounted in the usual manner in suitable fittingssupported by the upper end of casing spool 56. Positive chokes areusually installed in the wellhead assembly to reduce the pressure inflow lines exposed to damage by collision or storms. It will be apparentthat the particular wellhead assembly illustrated in FIGURE 3 is shownmerely for purposes of illustration, and this invention is notrestricted to any particular type of equipment used to make up thewellhead assembly.

A flow line 62 extends upwardly from the well head assembly through thesnorkel tube above the water line 64 for connection to a lubricator 66mounted in the upper end of the snorkel tube 44. Flow line 62 continuesupwardly to a separator unit 68 provided with suitable flow controls forcontrol of flow of oil from the separator. An oil line 70 from theseparator is connected to oil line 40, which extends upwardly from theoil storage tank 38, for delivery of oil from the separator 68 to thestorage tank. Mounted in the upper end of the snorkel tube above theseparator 68 is a turbine 72 driven by gas from the separator to operatea generator unit 74 which supplies electricity for a foghorn and lightunit 76 mounted on the top of the snorkel tube. If desired, thegenerator unit can be driven by LPG, compressed air, or other suitablemeans, or can be replaced by a suitable battery to supply electricityfor the foghorn and light unit. Manholes 78, 80, and 82 are providedalong the upper end of the snorkel tube above the water line 64 to allowaccess to the equipment supported in the snorkel tube.

In the operation of the well, oil produced from the well flows upwardlythrough line 62 into the separator 68 and downwardly from the separatorthrough oil line 70 into oil line 40 and then into the oil storage tank38. Oil flowing into oil storage tank 38 displaces water from the lowerend of the tank through vent line 42. Because storage tank 38 is openthrough line 42, it is at substantially the same pressure inside andout; hence, may be constructed of thin gauge metal. Oil is periodicallydelivered from the storage tank 38 to a barge through line 40 and valve84 by hydraulic pressure of water entering the storage tank. Servicework on the well can readily be accomplished through the lubricator 66when necessary. If repair to connections in the Christmas tree assembly60 is necessary, a workman can be lowered through the snorkel tube tomake the necessary repairs at atmospheric pressure.

This invention has been described for use on a wildcat well where it isnot known whether or not the well would penetrate productive formations.In such operations, the cost of the snorkel tube is delayed untilproduction from the formation is proven. Moreover, by plugging the wellin the manner described, the heavy mobile rig can be moved from locationand the high cost of rent of the rig while the snorkel tube isconstructed can be avoided. The snorkel tube can later be lowered intoposition and the cement plugs drilled from a less expensive rig.

When drilling into a proven reservoir, it is advantageous to install thesnorkel tube before the well is drilled, as is illustrated in FIGURE 5.Referring to FIGURE 5, the snorkel tube support 32 is lowered intoposition and secured in place by piles 34 driven into the ocean floor20. Snorkel tube 44 is then lowered from a drilling rig 86, illustratedas a floating rig, and either washed or driven for the desired depthinto the ocean floor. Thereafter a drill bit 88 is lowered through thesnorkel tube and the well drilled by conventional procedures. After thewell has been drilled, the casing within the snorkel tube 44 is cut off.As in the embodiment described with reference to FIGURES 1 through 4,the casing can be cut by means of a milling tool or a rotating abrasivejet operated from the rig 86. The height at which the well is cut offcan range from approximately the level of the ocean floor 20 up to themaximum height above ocean floor 20 at which the well casing willsafely'support the wellhead assembly. The wellhead assembly is installedand the flow lines and production apparatus connected in the mannerdescribed with respect to FIGURES 1 through 4. An alternative procedurewould'be to install the initial part of the wellhead assembly near theocean floor with blowout preventers bolted to the head, also near theocean floor level. After drilling, the blowout preventers would beremoved and the well completed at the ocean floor in conventionalmanner, except for sub-sea locations.

The installation of the wellhead assembly below the surface of the waterand preferably slightly above the ocean floor avoids the necessity of aplatform to support an otherwise long, slender well column. Because thesupport for the snorkel tube only supplies lateral bracing, it can be ofrelatively lightweight construction. Only the relatively small surfaceof the snorkel tube is exposed to waves, wind, and collision; thewellhead assembly and the Christmas tree are located out of danger atthe ocean floor. Flow lines extending to the surface of the'water wherethey may be damaged by collision or wave action do not contain wellfluids under high pressure, since there is a positive choke in thewellhead.

The snorkel tube, being of heavy-walled construction, providesprotection and support for production apparatus located at or above thesurface of the water, and being permanently installed, provides acontinuously open passage to the wellhead assembly. The flow lines bothabove and below'the wellhead assembly being vertical are readilyserviced by wire line equipment on an ordinary small reworkingrig.Service of a well can be performed immediately without special equipmentfor gaining access to the wellhead connections by workmen working atatmospheric pressure. Because the snorkel tube is driven deep into theocean floor, for example as much as 100 or more feet, the seeping ofwater upwardly through the snorkel tube to the level of the ocean flooris very slow, even though the body of water is 500 feet deep. Unlike theusual caisson, it is not necessary to maintain a high pressure in thesnorkel tube to exclude water.

I claim:

1. A method of completing a well below a body of water at least about 50feet deep comprising forcing a heavy-walled snorkel tube permanentlyencircling and separate from casing of the well downwardly into theground below the body of water whereby said snorkel tube is supported bythe ground and extends upwardly above the surface of the water, saidsnorkel tube having a diameter of approximately 40 to 72 inches topermit a workman to descend in the tube to install wellhead connections,pumping water out of the tube, cutting olf casing of the well adjacentthe bottom of the body of water, installing a wellhead assembly on theupper end of the casing, running a flow line from the wellhead assemblyupwardly through the tube to above the surface of the Water, andsupporting the flow line within the tube for delivery of well fluidsabove the surface of the water.

2. A method as set forth in claim 1 in which a positive choke isinstalled in the flow line at the wellhead assembly.

3. A method of completing a well below a body of water at least about 50feet deep comprising forcing a heavy-walled snorkel tube into the groundbelow the body of water a distance adequate to support the tube, saidtube permanently extending upwardly above the surface of the water andhaving a diameter of about 40' to 72 inches allowing lowering of workerstherethrough and installation of a wellhead assembly therein, lowering adrill bit through the tube and drilling the well to the desired depth,setting casing in the well, cutting off the casing within the tubeadjacent the bottom of the body of water, pumping water from the tube toexpose the upper end of the casing to the atmosphere, installing awellhead assembly on the upper end of the casing, running a flow linefrom the wellhead assembly upwardly through the tubeto above the surfaceof the water, and supporting the flow line within the tube for deliveryof well fluids above the surface of the water.

4. A method as set forth in claim 3 in which the flow line is extendedupwardly through the tube to a separator mounted in the upper end of thetube above the surface of the water.

5. A method of completing a Well extending into subterranean formationsbelow a body of water at least about 50 feet deep comprising drilling aborehole to the desired depth through the subterranean formations,setting casing in the borehole, temporarily plugging the casing belowthe bottom of the body of water, cutting off the easing at a levelbetween the bottom of the body of water and the maximum height at whichthe casing will safely support a wellhead assembly, forcing a unitaryheavy- Walled snorkel tube having a diameter of approximately 40 to 72inches permitting workers to descend therethrough into the ground belowthe body of water a distance adequate to support said tube and preventsubstantial seepage into the tube, said tube encircling and separatefrom the casing and permanently extending upwardly above the surface ofthe water, removing water from the tube to expose the upper end of thetube to the atmosphere, drilling the temporary plugs from the casing,installing a wellhead assembly on the upper end of the casing, running aflow line from the wellhead assembly upwardly through the tube to alevel above the surface of the water, and supporting the flow linewithin the tube for delivery of well fluids above the surface of thewater.

6. A method of completing a well in water at least about feet deepcomprising forcing a unitary heavynwalled snorkel tube having a diameterof approximately 40 to 72 inches adequate to permit lowering of workmentherethrough into the bottom of a body of water to a depth adequate tosupport the tube and prevent substantial seepage of water into the tube,said tube extending permanently upwardly above the surface of the water,cutting off adjacent the bottom of the body of water casing encircled bythe snorkel tube and extending downward to a subterranean formation,pumping water from the snorkel tube to lower the level of waterthereinto to below the upper end of the casing, lowering a workmanthrough the snorkel tube to the upper end of the casing, installing awellhead assembly on the upper end of the casing, running a flow line upthrough the snorkel tube and supporting the flow line by the snorkeltube for delivery of well fluids above the surface of the water, andbracing said snorkel tube against lateral movement at a location 50 to100 feet below the surface of the water.

'7. A method of completing a well in a body of water at least about 100feet deep, said well having casing extending downwardly into the groundfor a desired distance into a subterranean formation, comprising drivinga heavy-walled snorkel tube having a diameter of 40 to 72 inchesadequate to permit a man to descend in the tube and install wellheadequipment downwardly into the bottom of a body of water to a depthadequate to support said snorkel tube and prevent substantial seepage ofwater upwardly through the snorkel tube, said snorkel tube encirclingand separate from the casing and permanently extending upwardly abovethe surface of the body of water, laterally bracing the snorkel tube ata depth about 50 feet below the surface of the body of water, pumpingthe water out of the snorkel tube, lowering a workman in the snorkeltube, installing a wellhead assembly on the casing adjacent the bottomof the body of water, running fluid flow lines from the wellheadassembly upwardly through the snorkel tube to above the surface of thewater, and supporting the flow lines by the snorkel tube for delivery ofwell fluids above the surface of the water.

8. A method as set forth in claim 7 in which the snorkel tube is drivento refusal in the bottom of a body of water and piles are driven intothe bottom of the body of water to anchor a support providing lateralbracing of the snorkel tube.

9. A method of completing an oil well in a body of water at least 100'feet deep and producing oil therefrom comprising driving a heavy-walledsnorkel tube having a diameter in the range of 40 to 72 inches torefusal in the bottom of the body of water, said snorkel tubepermanently extending upwardly above the surface of the water, loweringa drill through the snorkel tube and drilling a hole to a desired depthinto a subterranean formation, setting casing in said hole, pumpingwater from the snorkel tube to expose casing at the level of the bottomof the body of water to atmospheric pressure, cutting off casing withinthe snorkel tube adjacent the bottom of the body of water, loweringworkmen through the snorkel tube and installing a wellhead assembly onthe casing adjacent the bottom of the body of water, running flow linesfrom the wellhead assembly upwardly through the snorkel tube to aseparator supported by the snorkel tube above the surface of the body ofwater, separating oil from gases delivered through the fiow line in theseparator, delivering oil from the separator to a storage tank atsubstantially the bottom of the body of water to displace oil from thelower end of said storage tank, and periodically delivering oil from thestorage tank to a receiver at the surface of the body of water.

10. A well extending from an underground fluidbearing formation upwardlyto a body of water at least about 50 feet deep at the surface comprisingcasing extending from the fluid-bearing formation upwardly to a levelslightly above the bottom of the body of water, a unitary permanentheavy-walled snorkel tube having an internal diameter of approximately40 to 72 inches permitting passage of workers therethrough extendingcontinuously from above the surface of the water downwardly into theground below the body of water a distance adequate to support the tubeand prevent substantial seepage of water into the tube, saidheavy-walled tube encircling and separate from the casing, a wellheadassembly connected to the upper end of the casing slightly above the 8bottom of the body of water, and a flow line extending upwardlythroughand supported by the tube for delivery of well fluids above thesurface of the water.

11. A wall as set forth in claim 10 in which a positive choke in thewellhead assembly controls fiow through the flow line.

12. An underwater well extending downwardly into subterranean formationbelow a body of water at least about 50 feet deep comprising casingextending for the desired depth into the subterranean formations, aheavywalled snorkel tube encircling and separate from the casing andextending from above the surface of the water into the ground below thebody of water to a depth adequate to support the tube and preventsubstantial flow of water into the tube, said tube having a diameterpermitting passage of men therethrough and installation of a wellheadassembly therein, a wellhead assembly connected to the upper end of thecasing slightly above the bottom of the body of water, a flow lineextending upwardly through the tube from the wellhead assembly, and aseparator mounted in the upper end of the tube above the water level,said flow lines being connected to the separator for delivery of wellfluids into the separator.

13. An underwater well as set forth in claim 12 in which the body ofwater is at least about feet deep and a well support engages the outersurface of the tube about 50 feet below the surface of the Water toprovide lateral support for the tube.

14. An underwater well as set forth in claim 12 in which the body ofwater is 100 to 600 feet deep and a Well support engages the outersurface of the tube about 50 to 100 feet below the surface of the waterto provide lateral support for the tube.

15. An underwater well extending into subterranean formations below abody of water at least about 100 feet deep comprising casing extendingfor the desired depth into said subterranean formations, a heavy-walledsnorkel tube encircling the casing and extending from above the surfaceof the water into the ground below said body of water whereby the groundsupports said snorkel tube, a wellhead assembly connected to the upperend of the casing at a level above the bottom of the body of water andbelow the surface of the water whereby the casing supports the wellheadassembly, a separator mounted in the upper end of the snorkel tube abovethe surface of the water, a flow line extending from the wellheadassembly upwardly through the snorkel tube to the separator, asupporting structure secured to and supported by the bottom of the bodyof water engaging the outer surface of the tube about 50 feet to 100feet below the surface of the water, an oil storage tank secured to saidsupporting structure, and an oil line extending downwardly from theseparator into the upper end of the oil storage tank, said oil storagetank having a vent in its lower end to permit flow of water into saidstorage tank.

16. A well in water at least about 100 feet deep comprising aheavy-Walled tube having a diameter of approximately 40 to 48 inchesdriven to refusal in the bottom of a body of water, said tube extendingupwardly above the surface of the water and being open to the atmosphereat its upper end, means laterally bracing the tube at a level at leastabout 50 feet below the surface of water, casing within the snorkel tubeand separate therefrom extending downwardly to the desired depth into asubterranean formation, a wellhead assembly mounted on the casingadjacent the bottom of the body of water, and a flow line extendingupwardly through the snorkel tube to above the surface of the body ofwater.

17. A method of drilling and completing an offshore Well in water atleast 50 feet deep comprising locating a drilling rig at the Well site,drilling the well to the target formation, setting casing in the well,testing the well for production, setting a plug in the well to preventupward flow of fluids through the well, cutting the casing slightlyabove the ocean floor, moving the drilling rig from the site, driving aheavy-walled tube having a diameter of 40 to 72 inches into the oceanfloor, said heavy-walled tube encircling and separate from the casingand extending from above the surface of the water into the ocean floor adistance adequate to support the tube and prevent flow of water into thelower end thereof, pumping water from the heavy-walled tube to exposethe ocean floor within the tube to atmospheric pressure, installing ablowout preventer on the casing slightly above the level of the oceanfloor, removing the plug from the well, and installing a wellheadassembly on the casing at a level slightly above the ocean floor.

18. A method of drilling and completing an offshore well in water atleast 50 feet deep comprising locating a drilling rig at the well site,setting conductor pipe extending from above the surface of the waterdownwardly into the ocean floor, lowering a drill through the conductorpipe and drilling to an intermediate depth, setting surface pipe in thewell, locating cement in the annulus between the surface pipe andconductor pipe from the bottom of the surface pipe to approximately thelevel of the ocean floor, filling said annulus above the cement withsand, drilling the well to the target formation and setting casing inthe well, testing the well for production, setting a plug in the well toprevent upward flow of fluids through the well, cutting the casing,surface casing, and conductor pipe at a level slightly above the oceanfloor, moving the drilling rig from the site, driving a heavy-walledtube having a diameter of 40 to 72 inches into the ocean floor, saidheavy-walled tube encircling and separate f om the casing and extendingfrom above the surface of the water into the ocean floor a distanceadequate to support the tube and prevent flow of water into the lowerend thereof, pumping water from the heavy-walled tube to expose theocean floor within the tube to atmospheric pressure, installing ablowout preventer on the casing slightly above the level of the oceanfloor, removing the plug from the well, and installing a wellheadassembly on the casing at a level slightly above the ocean floor.

References Cited UNITED STATES PATENTS 2,631,558 3/1953 Harris 114-.52,684,575 7/1954 Pryor et a1 1758 X 2,699,321 1/1955 Nelson 17582,731,168 1/1956 Watts 114.5 2,854,215 9/1958 Cox et al 61-82 X2,906,500 9/1959 Knapp et al 166.5 2,988,144 6/1961 Conrad 166-.53,020,956 2/1962 Suderow 1755 X 3,125,171 3/1964 Stewart 175-9 X3,202,218 8/1965 Watts et a1. 166.5 3,221,816 12/1965 Shatto et al.166.5

CHARLES E. OCONNELL, Primary Examiner.

ERNEST R. PURSER, Examiner.

RICHARD E. FAVREAU, Assistant Examiner.

1. A METHOD OF COMPLETING A WELL BELOW A BODY OF WATER AT LEAST ABOUT 50FEET DEEP COMPRISING FORCING A HEAVY-WALLED SNORKEL TUBE PERMANENTLYENCIRCLING AND SEPARATE FROM CASING OF THE WELL DOWNWARDLY INTO THEGROUND BELOW THE BODY OF WATER WHEREBY SAID SNORKEL TUBE IS SUPPORTED BYTHE GROUND AND EXTENDS UPWARDLY ABOVE THE SURFACE OF THE WATER, SAIDSNORKEL TUBE HAVING A DIAMETER OF APPROXIMATELY TO 72 INCHES TO PERMIT AWORKMAN TO DESCEND IN THE TUBE TO INSTALL WELLHEAD CONNECTIONS, PUMPINGWATER OUT OF THE TUBE, CUTTING OFF CASING OF THE WELL ADJACENT THEBOTTOM OF THE BODY OF WATER, INSTALLING A WELLHEAD ASSEMBLY ON THE UPPEREND OF THE CASING, RUNNING A FLOW LINE FROM THE WELLHEAD ASSEMBLYUPWARDLY THROUGH THE TUBE TO ABOVE THE SURFACE OF THE WATER, ANDSUPPORTING THE FLOW LINE WITHIN THE TUBE FOR DELIVERY OF WELL FLUIDSABOVE THE SURFACE OF THE WATER.